This invention relates to a vehicle height adjusting apparatus for use in a vehicle such as an automobile.
Conventional vehicle height adjusting apparatus mounted on a vehicle such as an automobile comprises air bags or air springs provided between sprung and unsprung masses of the vehicle, and the height of the vehicle is adjusted by supplying or discharging pressurized air into or from the air bags, thereby adjusting the height of the vehicle. An air compressor is connected to the air spring for supplying pressurized air to the air bags. The air bags are usually associated with hydraulic dampers. Such apparatus generally operates satisfactorily. However, there is a shortcoming that the air compressor will sometimes be operated for an excessively long time period when an excessively heavy load is mounted on the vehicle, or when a failure or leakage occurs in the circuit connecting the air bags with the air compressor. In such case, the height of the vehicle cannot be adjusted to the predetermined level, and the air compressor may fail due to the overheating.
Its has been proposed to overcome this shortcoming by detecting the operating time period of supplying pressurized air into the air bags and stopping the supply of the pressurized air when the operating time exceeds a predetermined time. However with this procedure the air compressor will sometimes be stopped even though the air compressor has not been overheated.